The present invention relates generally to an optical system, and more particularly related to a method and system for predicting the directions and intensities at which light scatters from a surface, such that a scattering prediction includes a substantially continuous solution over a set of scattering angles that includes specular and non-specular scattering angles, wherein the scattering prediction may be used to generate improved optical systems and improved scattering simulations.
Scattering of stray light in optical devices, such as lenses, telescopes and the like, is a phenomenon that optical designers generally prefer to reduce. Stray light scattering generally refers to the scatter of stray light in an optical system from a surface, such as body portions of lens or telescope. Stray light in an optical system includes light that has separated from an optical signal and often travels along undesired paths. For example, stray light in the lens of a camera can cause photographic images to be formed that have aberrant light features that were not present in a photographed scene.
Designers of optical system typically aim to reduce stray light generation and, once generated, to lower its degrading effect. To lower the degrading effects of stray light scatter, optical designers strive to generate relatively accurate predictive models of light scattering from surfaces. In generating relatively accurate models of light scattering from surfaces, stray light scattering may be better understood and compensated for in the design of optical systems. Models for stray light scattering can be incorporated in optical design programs that show the deleterious effects of stray light scattering as predicted by the models. Stray light scattering estimations calculated prior to building an optical system, can be used to improve final designs to build improved optical systems.
While understanding stray light scattering in optical systems may be used to improve optical systems through improved optical system designs, models for stray light scattering can also be used in light simulation systems, such as in a computer graphics program (e.g., video games, and movie animations). Relatively accurate prediction of stray light scattering from a surface can be used in a computer graphic to simulate scattering from a surface that is substantially realistic.
Predictive light scattering has historically been a diagnostic tool in the field of surface roughness measurements. It was realized relatively early in the study of scattering that the distribution of scattering from a surface can be related to the power spectral density of variations in surface heights of the surface. Generating relatively accurate models of power spectral density as related to surface height variation has provided for the extraction of surface height information from measured power spectral densities to characterize surfaces. See, for example, the studies of James Elmer Harvey reported in Light-Scattering Characteristics of Optical Surfaces, dissertation submitted to the Faculty of the Committee on Optical Sciences, The University of Arizona, 1976, herein Harvey '76. While predictive models of scattering have been used with some success in predicting scattering from surfaces and thus providing extraction of surface height information (e.g., degree that a surface resembles a diffraction grating pattern) from a surface, predictive models of scattering have generally provided non-continuous solutions, for example, between specular and non-specular regions of scatter. Scattering regions for which known models of scattering break down are often compensated for with empirical scattering data or intuitively estimated. However, compensating empirically or intuitively for the shortcomings of known models of scattering tends to be relatively time consuming and often costly as technicians and/or engineers often fill in manually, regions for which known scattering models break down.
Measurement techniques and models for stray light scattering have historically been non-differential techniques. Non-differential techniques and models yield results that often include scattering information of a particular lab setup as well as scattering information of a sample. Separation of lab setup information from sample information in both measurement techniques and models of stray light scattering is often intuitively or empirically carried out. Addition steps of intuitive and/or empirical processing for isolating scattering information from lab setup information is often costly, time consuming, and may produce less than optimal results.
Accordingly, what is needed are improved methods and systems for predicting scattering of stray light from surfaces and more specifically what is needed are models of stray light scattering that generate continuous scattering solutions over a set of scattering angles that includes specular and non-specular scattering angles, wherein the scattering predictions may be used in computer design and computer simulations to generate improved optical systems and improved scattering simulations.